The present invention relates to a charged particle beam control element for controlling a trajectory or a cross-sectional shape of a charged particle beam by an electrostatic field, a method of fabricating the charged particle beam control element, and a charged particle beam apparatus.
The conventionally well-known charged particle beam control elements for controlling the trajectory or the cross-sectional shape of the charged particle beam by the electrostatic field include electrostatic deflectors, electrostatic lenses, stigmators, and so on.
FIG. 11 is a top plan view to show a conventional electrostatic deflector 100. FIG. 12A is a figure to show an Axe2x80x94A cross section of FIG. 11 and FIG. 12B a figure to show a Bxe2x80x94B cross section of FIG. 11.
The electrostatic deflector 100 has octupole metal electrodes 101 (see FIG. 11). Each of the metal electrodes 101 is fixed to the inside of an insulating sheath 102 with fixing screws 103, 104 (see FIG. 12A). A voltage-applying wire 105 to each metal electrode 101 is directly fixed to the corresponding metal electrode 101 with a wiring screw 106 (see FIG. 12B).
In this electrostatic deflector 100, an electrostatic field is established according to voltages applied to the respective metal electrodes 101 inside a space 107 surrounded by internal surfaces 101a of the respective metal electrodes 101. Accordingly, the charged particle beam passing along the center axis Z in the space 107 is deflected according to the electrostatic field established in the space 107.
Each of clearances 108 between adjacent metal electrodes 101 is not of the shape of a straight line, but of the shape bent twice and then reaching the insulating sheath 102. This is for the purpose of keeping exposed portions 109 of the insulating sheath 102 off direct view from the charged particle beam passing the space 107. This structure prevents charge-up of the insulating sheath 102 and allows the electrostatic field in the space 107 to be precisely controlled by the voltages applied to the respective metal electrodes 101.
The above electrostatic deflector 100, however, had the problems of the complex structure, the large number of components, and difficulties in reduction of cost and size.
The octupole metal electrodes 101 constituting the electrostatic deflector 100 are constructed by first screwing a metal cylinder to the inside of the insulating sheath 102 and dividing the cylinder into the electrodes. For this reason, it was difficult to enhance dividing angle accuracy of the metal electrodes 101. For the same reason, it was also difficult to enhance the circularity of the space 107 surrounded by the internal surfaces 101a of the metal electrodes 101.
Thus proposed recently was use of film electrodes deposited on an insulator by a surface treatment of plating or the like (plating electrodes) instead of the above metal electrodes 101 (for example, as described in Japanese Patent Application Laid-Open No. H02-247966). The electrostatic deflectors using the plating electrodes obviate the need for screwing of the electrodes, which can decrease the number of components and decrease the size.
In the electrostatic deflectors using the plating electrodes, if the voltage-applying wires are directly fixed to the plating electrodes by screwing as in the case of the conventional electrostatic deflector 100 described above, the surfaces of the plating electrodes can be perforated with holes. If the plating electrodes should have holes the electrostatic field distribution could be distorted in the space in which the charged particle beam passes, and it would result in failing to control deflection of the charged particle beam with high accuracy.
For this reason, the electrostatic deflector disclosed in the application Laid-Open No. H02-247966 is constructed to prevent the surfaces of the plating electrodes from being perforated in such a manner that support portions of an insulator with the plating electrodes formed thereon are projected out, together with the plating electrodes, from an end of the insulating sheath and that the voltage-applying wires are connected to the projecting portions. However, this wiring structure was complex and there was the possibility that coatings (insulator) of the voltage-applying wires connected to the projecting portions could be viewed through clearances between adjacent plating electrodes.
There were also desires for construction using the plating electrodes in the other charged particle beam control elements (such as the electrostatic lenses and the like) as well as the aforementioned electrostatic deflectors. Under such circumstances, there were desires for some idea about how to connect the voltage-applying wires to the plating electrodes.
An object of the present invention is to provide a charged particle beam control element enabling the connection of the voltage-applying wires to the electrodes in simple structure while maintaining the surfaces of the electrodes formed on the insulator by the surface treatment of plating or the like with high accuracy, a method of fabricating the charged particle beam control element, and a charged particle beam apparatus.
A charged particle beam control element according to the present invention is a charged particle beam control element for controlling a trajectory of a charged particle beam by an electrostatic field, which comprises: a cylindrical base having a plurality of electrode portions formed on an internal surface thereof; and insulating portions, which are disposed at respective locations not exposed to a passing area of the charged particle beam surrounded by the internal surface, separate the electrode portions from each other.
Since the plurality of electrode portions formed on the internal surface are separated from each other by the insulating portions in this way, the internal surface defining the passing area of the charged particle beam can be readily machined in any desired shape. Since the insulating portions are not exposed to the passing area of the charged particle beam, the charged particle beam can be controlled more accurately without charging the insulating portions up by the charged particle beam.
The above charged particle beam control element may also be so configured that a plurality of grooves extending from one end to the other end of the base are formed on the internal surface and that a cross-sectional shape of each groove is bent and each insulating portion is formed in a deepest area of the groove.
When the insulating portions are formed in the grooves extending from one end to the other end of the base in this way, the electrode portions formed on the internal surface can be separated from each other. When the insulating portion is formed in the deepest area of each bent groove, the insulating portion can be kept from being exposed to the passing area of the charged particle beam.
The above charged particle beam control element may also be so configured that a through hole is formed so as to penetrate the base between a peripheral surface of the base and each groove and that an electroconductive portion is formed on an internal surface of the through hole.
When the conductive portion is formed on the internal surface of the through hole penetrating the base from the peripheral surface to the groove, it becomes unnecessary to form the conductive portion on the internal surface defining the passing area of the charged particle beam and thus it becomes feasible to keep the internal surface smooth. When the through hole is used as a screw hole for fixing the base, the structure of the charged particle beam control element can be simplified.
The above charged particle beam control element may also be so configured that the through hole is not exposed to the passing area of the charged particle beam.
When the through hole is formed so as not to be exposed to the passing area of the charged particle beam in this way, it becomes feasible to weaken the effect of electric current flowing in the conductive portion on the passing area of the charged particle beam.
A fabrication method of a charged particle beam control element according to the present invention is a method of fabricating a charged particle beam control element for controlling a trajectory of a charged particle beam by an electrostatic field, the method comprising: a groove forming step of forming on an internal surface of a cylindrical base, a groove extending from one end to the other end of the base and having a bent cross-sectional shape; a conductive member depositing step of depositing an electroconductive member on the internal surface including the groove; and an insulating portion forming step of forming an insulating portion by removing the electroconductive member deposited in a deepest area of the groove, from one end toward the other end of the base.
When the conductive member is deposited on the internal surface in the conductive member depositing step after the formation of the groove in the base in the groove forming step as described above, the electrode portion and the conductive portion can be formed readily. Then the electrode portion can be separated into plural regions by removing the conductive member deposited in the deepest area of the groove in the insulating portion forming step.
The above charged particle beam control element fabrication method may also be arranged to further comprise a conductive member grinding step of grinding a surface of the electroconductive member deposited on the internal surface so that the cross-sectional shape of the internal surface becomes complete round, after the conductive member depositing step.
When the surface of the electroconductive member is ground after the deposition of the electroconductive member in this way, the internal surface defining the passing area of the charged particle beam can be made close to complete round.
The above charged particle beam control element fabrication method may also be arranged to further comprise a conductive member grinding step of grinding a surface of the electroconductive member deposited on the groove in order to adjust a position of an electrode portion, after the conductive member depositing step.
The position of the electrode portion can be adjusted by grinding the surface of the conductive member after the deposition of the conductive member in this way.
The above charged particle beam control element fabrication method is preferably arranged to further comprise a through hole forming step of forming a through hole penetrating the base between a peripheral surface of the base and the groove, between the groove forming step and the conductive member depositing step.
Another charged particle beam control element according to the present invention is a charged particle beam control element comprising: a cylindrical base having an electrode portion formed on an internal surface thereof; a first electroconductive member placed on an internal surface of a communicating hole formed so as to establish communication between one end of the base and a through hole for fixing the base, formed in a peripheral surface of the base; and a second electroconductive member placed on the one end of the base so as to connect the first electroconductive member with the electrode portion.
When the charged particle beam control element has the structure in which the communicating hole for establishing communication between the through hole and one end of the base is formed in the base and the element has the second conductive portion connecting the first conductive portion placed on the internal surface of the communicating hole with the electrode portion defining the passing area of the charged particle beam, the surface of the electrode portion (internal surface) can be kept smooth.
A charged particle beam apparatus according to the present invention comprises the above charged particle beam control element, and irradiation means for implementing irradiation with a charged particle beam controlled by the charged particle beam control element.
The charged particle beam apparatus having the above charged particle beam control element as described above can realize the charged particle beam apparatus of simple structure while keeping the surface of the electrode portions formed on the internal surface of the charged particle beam control element with high accuracy.